Beam splitting hand off systems architecture

ABSTRACT

A beam splitting hand off systems architecture and method for using the same are disclosed. In one embodiment, the method comprises: generating a first beam with a single electronically steered flat-panel antenna to track a first satellite; generating a second beam with the single electronically steered flat-panel antenna to track a second satellite simultaneously while generating the first beam to track the first satellite; and handing off traffic from the first satellite to the second satellite.

PRIORITY

The present patent application is a continuation of and claims benefitof U.S. patent application Ser. No. 16/432,624, filed on Jun. 5, 2019and entitled “BEAM SPLITTING HAND OFF SYSTEMS ARCHITECTURE,” whichclaims priority to and incorporates by reference the correspondingprovisional patent applications No. 62/681,552, titled, “BEAM SPLITTINGHAND OFF SYSTEMS ARCHITECTURE,” filed on Jun. 6, 2018.

FIELD OF THE INVENTION

Embodiments of the present invention relate to the field of wirelesscommunication; more particularly, the embodiments of the presentinvention relate to generating multiple beams simultaneously with asingle satellite antenna to facilitate handing off communication betweentwo satellites.

BACKGROUND OF THE INVENTION

A satellite terminal attempting to stay in communication with aconstellation of nonstationary satellites can only point to a givensatellite while that satellite is within the terminal's field of view.When the satellite leaves the field of view, the terminal must point toa different satellite that has recently entered the field of view. Withonly a single beam to point to any given satellite at any one time, theRF connection will be lost during the transition to a differentsatellite. That is, the satellite will have to break its connection withthe satellite leaving its field of view so that it can make a connectionwith a new satellite that is entering or already in its field of view.This break-before-make connection results in a data outage, caused bytime for the antenna to switch pointing angles, time for the trackingalgorithms to optimize the pointing on the new satellite, time for themodem to lock to the new carrier, and time for the network tore-establish end-to-end connection.

SUMMARY OF THE INVENTION

A beam splitting hand off systems architecture and method for using thesame are disclosed. In one embodiment, the method comprises: generatinga first beam with a single electronically steered flat-panel antenna totrack a first satellite; generating a second beam with the singleelectronically steered flat-panel antenna to track a second satellitesimultaneously while generating the first beam to track the firstsatellite; and handing off traffic from the first satellite to thesecond satellite.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given below and from the accompanying drawings of variousembodiments of the invention, which, however, should not be taken tolimit the invention to the specific embodiments, but are for explanationand understanding only.

FIG. 1 is a flow diagram of one embodiment of a method for using asatellite antenna for communication.

FIG. 2 is a flow diagram of one embodiment of a method for using asatellite antenna for communication.

FIG. 3 illustrates one embodiment of a beam splitting antenna system.

FIG. 4 is a block diagram of an alternative beam splitting antennasystem.

FIG. 5A is an antenna beam switching timing diagram to track and handoff satellites.

FIG. 5B illustrates an example of a transmit (Tx) beam splitting andhandoff and corresponding timing diagram.

FIG. 6 illustrates the schematic of one embodiment of a cylindricallyfed holographic radial aperture antenna.

FIG. 7 illustrates a perspective view of one row of antenna elementsthat includes a ground plane and a reconfigurable resonator layer.

FIG. 8A illustrates one embodiment of a tunable resonator/slot.

FIG. 8B illustrates a cross section view of one embodiment of a physicalantenna aperture.

FIGS. 9A-D illustrate one embodiment of the different layers forcreating the slotted array.

FIG. 10 illustrates a side view of one embodiment of a cylindrically fedantenna structure.

FIG. 11 illustrates another embodiment of the antenna system with anoutgoing wave.

FIG. 12 illustrates one embodiment of the placement of matrix drivecircuitry with respect to antenna elements.

FIG. 13 illustrates one embodiment of a TFT package.

FIG. 14 is a block diagram of one embodiment of a communication systemhaving simultaneous transmit and receive paths.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providea more thorough explanation of the present invention. It will beapparent, however, to one skilled in the art, that the present inventionmay be practiced without these specific details. In other instances,well-known structures and devices are shown in block diagram form,rather than in detail, in order to avoid obscuring the presentinvention.

Embodiments of the invention include a method and system architecture totrack nonstationary and stationary satellite constellations and handoffsatellite traffic between two simultaneous and independent beamsgenerated from a single electronically steered flat antenna such thatconnectivity is maintained throughout the transition from one satelliteto another. In another embodiment, this includes the handoff of transmittraffic. By using the techniques disclosed herein, make-before-breakhandoffs between non-stationary, stationary satellite or spacecraft areenabled.

The techniques described herein include a number of innovations, such ofwhich are described below. For example, in one embodiment, two beams aresimultaneously generated with a single electronically steered flatantenna to track two satellites within the constellation and thenseamlessly hand off traffic from an initial satellite to a new,subsequent satellite.

In one embodiment, one electronically steered antenna is used forexecuting make-before-break connections in which an RF connection ismade with the new satellite before the RF link is broken with theexisting satellite.

FIG. 1 is a flow diagram of one embodiment of a method for using asatellite antenna for communication. In one embodiment, the processesare performed by processing logic that may comprise hardware (e.g.,circuitry, dedicated logic, etc.), software (e.g., software running on achip), firmware, or a combination of the three. In one embodiment, thesatellite antenna is a flat-panel antenna. In another embodiment, thesatellite antenna is an electronically steered flat-panel antenna.Examples of such electronically steered flat-panel antennas aredescribed in more detail below.

Referring to FIG. 1, the process begins by processing logic operating anantenna (e.g., an electronically steered flat-panel antenna) in asingle-beam configuration (or mode) in which the antenna is generating asingle receive beam during tracking to track a first satellite(processing block 101). In one embodiment, operating the antenna in thesingle-beam configuration includes generating an electronically steeredantenna beam pattern for beamforming, sending the beam pattern to anantenna aperture of an electronically steered flat-panel antenna havinga set of RF radiating antenna elements (e.g., surface scatteringmetamaterial antenna elements, such as, for example, but not limited to,those described below), and generating a receive beam with the RFradiating antenna elements based on the antenna pattern.

Subsequently, processing logic operates the antenna in a multi-beamconfiguration (e.g., a dual-receive beam configuration) in which theantenna is generating two or more receive beams during tracking to trackmultiple satellites, including generating at least one additionalreceive beam with the antenna to track a second satellite simultaneouslywhile continuing to generate a receive beam pointing to and tracking thefirst satellite (processing block 102). In one embodiment, when themulti-beam mode is in a dual-beam mode, the antenna generates tworeceive beams for pointing to and tracking two satellites, where the twosatellites include the satellite to which the antenna was pointing andtracking during the previous single-beam configuration and a newsatellite from which the antenna acquired a signal and began trackingwith the second beam while in the multi-beam configuration.

Thereafter, after tracking of an additional satellite, processing logicreturns to operating the antenna in the single-beam configuration withthe single receive beam pointing to and tracking the new satellite forwhich a signal was acquired during the multi-beam configuration,including handing off traffic from the satellite being tracked while inthe previous single-beam configuration to the new satellite (processingblock 103). In one embodiment, handing off traffic is performedseamlessly such that connectivity is maintained throughout thetransition from the previously tracked satellite to the new satellite.

FIG. 2 is a flow diagram of one embodiment of a method for using asatellite antenna for communication. In one embodiment, the processesare performed by processing logic that may comprise hardware (e.g.,circuitry, dedicated logic, etc.), software (e.g., software running on achip), firmware, or a combination of the three. In one embodiment, thesatellite antenna is a flat-panel antenna. In another embodiment, thesatellite antenna is an electronically steered flat-panel antenna.Examples of such electronically steered flat-panel antennas aredescribed in more detail below.

Referring to FIG. 2, the process begins by processing logic controllingan electronically steered flat-panel antenna to generate a singlereceive beam pointing to and tracking a first satellite using a firstset of RF radiating antenna elements (e.g., surface scatteringmetamaterial antenna elements, such as, for example, but not limited to,those described below) on an antenna aperture of the antenna (processingblock 201). In one embodiment, processing logic controls the antenna bygenerating an electronically steered antenna pattern for beamforming,sending the receive beam pattern to an antenna aperture of the antennathat has a set of RF radiating antenna elements, and generating thesingle receive beam with the first set of RF radiating antenna elementsbased on the pattern.

While tracking the first satellite, processing logic makes adetermination to switch the antenna into a two-receive beamconfiguration in which the antenna is generating first and secondreceive beams simultaneously (processing block 202). In one embodiment,this determination to switch the antenna into a two-beam configurationis made when the antenna is leaving the field of view of the firstsatellite and needs to find a second satellite for continuingcommunications.

After determining to switch to a two-receive beam configuration,processing logic controls the antenna to generate a second beam toacquire a signal from a second (different) satellite while continuing togenerate the first beam to track the first satellite, where the firstand second receive beams are generated simultaneously using two sets ofRF radiating antenna elements, respectively, of an antenna aperture(processing block 203) and then acquires a signal of the secondsatellite using the second beam (processing block 204). In this case,the first beam remains pointing to and tracking the first satellitewhile the second beam is pointing to the second satellite.

In one embodiment, the first and second beams point at carriers that areat different frequencies. In one embodiment, the first and second beamshave different antenna gains, wherein gain for the second beam is lowerthan the gain for the first beam. In one embodiment, this occurs whenthe second beam is used for acquiring the signal from the secondsatellite. In one embodiment, the second beam is wider than the firstbeam when used for acquiring the signal from the second satellite. Inone embodiment, the beam is made wider to allow capture of a signal whenthere is some uncertainty as to the exact location of the signal. In oneembodiment, the amount to widen the beam depends on the degree ofuncertainty about the location of the signal. In one example embodiment,if the beam during pointing and tracking is less than 2 degrees wide,then the beam for acquisition is broadened to about (but not limited to)10 degrees wide. Note that this is merely an example, and the beam isnot limited to being 10 degrees wide during acquisition. However, if thebeam is too wide there is a risk of picking up another satellite.

In one embodiment, the RF radiating antenna elements of the two sets forgenerating the two beams simultaneously are different from each otherbut are part of the RF radiating antenna elements of the antenna. In oneembodiment, the two sets of RF radiating antenna elements for generatingthe two beams simultaneously when operating the antenna in adual-receive beam configuration are part of, or comprise all of, the RFradiating antenna elements that are used for generating one beam whenoperating the antenna in a single-beam configuration.

In one embodiment, the two sets of RF radiating antenna elements have adifferent number of RF radiating antenna elements (e.g., 75% of theantenna elements used for generating the first beam and 25% of theantenna elements used for generating the second beam during signalacquisition). The number of elements used to generate each of the beamsdepends on the satellites for a minimum gain level. In one embodiment,for specific satellites/scenarios, there could be 10+dB signal-to-noiseratio (SNR) so the two radiation patterns could be offset by that much.However, in other scenarios, differences of more or less than 10+dB maybe sufficient.

In one embodiment, the antenna aperture includes a set of RF antennaelements dedicated for use in signal acquisition of a new satellite withthe second beam.

In one embodiment, the second and third sets of RF radiating antennaelements are in rings around a central feed for a feed wave, and furtherwherein each ring of the second set of RF radiating antenna elements isbetween rings of RF radiating antenna elements in the third set of RFradiating antenna elements. In one embodiment, the second and third setsof RF radiating antenna elements are in rings around a central feed fora feed wave, with the second set of RF radiating antenna elements beingin rings closest to the central feed in comparison to rings of the thirdset of RF radiating antenna elements. Examples of the rings aredescribed in more detail below. For example, in FIG. 6, every odd oreven numbered ring may be used for the second set of RF radiatingelements, while the other rings are used for the third set of RFradiating elements. Similarly, in FIG. 6, the set of rings closest tothe cylindrical feed may be used for the second set of RF radiatingelements, while the other rings are used for the third set of RFradiating elements.

In one embodiment, the second pattern that is applied to the RFradiating elements to point the second receive beam points to apredicted location of the second satellite. In one embodiment, thepredicted location is based on commanded two-line elements (TLE).

After signal acquisition of the second satellite, processing logiccontrols the antenna to operate in a dual-receive beam configuration(mode) in which the antenna is generating the first and second receivebeams simultaneously to track the first and second satellites,respectively (processing block 205). In one embodiment, when in adual-receive beam mode, the antenna generates two receive beams forpointing to and tracking two satellites simultaneously, where the twosatellites include the satellite to which the antenna was pointing andtracking during the single-beam configuration prior to signalacquisition of the second satellite and the second satellite from whichthe antenna acquired a signal and began tracking while in the multi-beamconfiguration.

Thereafter, after tracking of the second satellite has begun, processinglogic returns to operating the antenna in the single-beam configurationwith the single receive beam pointing at and tracking the secondsatellite, including handing off traffic from the first satellite to thesecond satellite (processing block 206). In one embodiment, handing offtraffic is performed seamlessly such that connectivity is maintainedthroughout the transition from the first satellite to the secondsatellite. In one embodiment, the handing off of traffic between thefirst and second satellites occurs in a manner well-known in the art ofswitching traffic between satellites.

Techniques described above are performed by an antenna that is used insatellite communication. In one embodiment, the antenna comprises anelectronically steered flat-panel antenna aperture with a plurality ofelectronically controlled radio frequency (RF) radiating antennaelements (e.g., surface scattering metamaterial antenna elements orresonators such as, for example, described in more detail below), andone or more processors coupled to the antenna aperture to control theantenna aperture such that the antenna aperture generates a first beamwith the antenna aperture to track a first satellite, generates a secondbeam with the antenna aperture to track a second satellitesimultaneously while generating the first beam, and hands off trafficfrom the first satellite to the second satellite. In one embodiment, theprocessor hands off traffic seamlessly between the first and secondsatellites such that connectivity is maintained throughout thetransition from the first satellite to the second satellite.

In one embodiment, prior to generating the second beam to track thesecond satellite, a processor controls the antenna aperture to generatethe second beam to acquire a signal from the second satellite whilegenerating the first beam. In one embodiment, the processor generatesfirst and second patterns to apply to first and second sets of first andsecond sets of radio-frequency (RF) radiating antenna elements,respectively, of the antenna aperture to generate the first and secondbeams, respectively, to point at carriers that differ in frequency.

FIG. 3 is an example of a satellite antenna architecture that is capableof generating one receive beam or two receive beams simultaneously tofacilitate handing off communication between two satellites.

Referring to FIG. 3, host processor 302 receives satellite location(e.g., latitude and longitude) and polarization information, and inresponse to these inputs, performs antenna receive pointing bygenerating pointing and tracking information that is provided to andcontrols antenna elements of an antenna aperture of antenna systemmodule (ASM) 301. Examples of such an antenna aperture having RFradiating antenna elements (e.g., surface scattering antenna elements orresonators) are described in more detail below. In one embodiment, thepointing and tracking information is associated with electronicallycontrolled antenna wave patterns that are used to control the RFradiating antenna elements as described herein.

In one embodiment, the pointing and tracking information comprises apointing angle (e.g., theta, phi), frequency information and symbol rateinformation. The theta range may be [0,90] degrees, the phi range may be[0,360] degrees. In one embodiment, host processor 302 also generatespolarization values that are provided to the antenna aperture of ASM301. The polarization value may range from [0,360] degrees. In oneembodiment, the polarization values are generated by host processor 302in a manner well-known in the art.

The receive portion of antenna aperture of ASM 301 uses the new pointingangle to generate a beam to obtain an RF signal from a satellite andprovide it to modem 303. In one embodiment, when only one set ofpointing information is sent by host processor 302 to ASM 301, theantenna aperture of ASM 301 generates one receive beam using all of theRF radiating antenna elements that are designated for receivetransmissions (as opposed to those used for transmit) and the receivebeam is used to obtain the RF signal from the satellite.

In response to a received RF signal, modem 303 generates receive metrics(e.g., SNR, C/N, etc.) regarding the Rx signal being received. In oneembodiment, the receive metrics indicate whether the satellite signalhas been found based on whether the signal meets one or morepredetermined criterion (e.g., SNR or C/N greater than a predeterminedthreshold) in a manner well-known in the art.

In one embodiment, host processor 302 provides two sets of pointing andtracking information to the antenna aperture of ASM 301, where each setof pointing and tracking information is for controlling a different setof antenna elements of the antenna aperture of ASM 301, to enable ASM301 to generate beams 1 and 2. That is, host processor 302 sends twosets of pointing and tracking information to ASM 301 to generate tworeceive beams simultaneously using different sets of antenna elements ofthe antenna aperture of ASM 301. In one embodiment, the two receivebeams are generated by dividing one set of antenna elements into twogroups (e.g., every other ring of antenna elements, or every otherantenna element in a ring or distribution, or randomly distributed) andforming two independent beams, at the same frequency or at differentfrequencies within the dynamic bandwidth of that element type. This canbe at different thetas or at the same theta.

In one embodiment, in order to generate an electronically steeredantenna pattern, host processor 302 sends commands to an antenna controlprocess (ACP) module on ASM 301 to start tracking a target satellite,and in response to the information, the ACP module sends setupinformation and continuously calculates and sends pointing vectors to aservice. In one embodiment, the ACP module sends setup and pointinginformation comprised of an operating frequency (e.g., f1, f2) andpolarization values for the antenna aperture at ASM 301 as setupinformation and a pointing vector having theta, phi and linearpolarization angle (LPA) values as the pointing information to thepattern generation service.

In response to the setup and pointing information, the service providesa plurality of electronically steered antenna patterns that controlantenna elements (e.g., RF radiating antenna elements (e.g.,metamaterial scattering antenna elements)) of the antenna aperture toform the two receive beams. In one embodiment, this service comprises asoftware service that is executed by one or more processors of ASM 301.In another embodiment, this service comprises hardware on ASM 301.

In one embodiment, pattern generation service loads beamformingparameters into an FPGA corresponding to the patterns. In response, theFPGA outputs the pattern to the antenna elements of the electronicallysteered antenna in the form of digital-to-analog (DAC) values (for eachpattern). More specifically, a DAC value for each antenna element in theantenna aperture is calculated by the FPGA using the beamformingparameters provided by the pattern generation service. The FPGA thenoutputs control signals to the antenna elements to drive the calculatedpattern. In one embodiment, the DAC values control thin film transistors(TFTs) in order to control the antenna elements of the antenna aperture(not shown) to generate a beam. Examples of TFT and their control aredescribed in more detail below.

After each of the two beams, beam 1 and beam 2, has been formed inresponse to patterns generated by the pattern generation service of ASM301, a receiver on ASM receives a signal back from the use of eachreceive beam and provides that to diplexer 305. From diplexer 305, thesignals are processed by Low Noise Block (LNB) 306, which performs anoise filtering function and a down conversion and amplificationfunction in a manner well-known in the art. Note that in FIG. 3, in oneembodiment, as the signals from the two beams are different infrequencies, LNB 306 covers both frequencies simultaneously. In oneembodiment, LNB 306 is in an out-door unit (ODU). In another embodiment,LNB 306 is integrated into the antenna apparatus.

After signal processing by LNB 306, the signal is sent to a directionalcoupler 344, which couples energy from the received signal output fromLNB 306 to an Rx power divider 343 and to modem 303 (as signal 331). Inone embodiment, directional coupler 344 is a 10 dB directional coupler;however, other couplers may be used.

Rx power divider 343 splits the signal received from directional coupler344 into two signals and sends one signal to tracking receiver 341 andthe other signal to tracking receiver 342. In one embodiment, thesignals are split based on frequency, such that the signals associatedwith beam 1 are sent to one of tracking receivers 341 and 342, while thesignals associated with beam 2 are sent to the other of trackingreceivers 341 and 342. Note that if the antenna is operating in asingle-beam mode and only generating one receive beam, then Rx powerdivider 343 provides the one signal to only one of tracking receivers341 or 342 and no signal to the other. In one embodiment, Rx powerdivider is a diplexer. Alternatively, Rx power divider 343 comprises apower splitter or a frequency adjustable filter.

In response to signal 331, modem 303 processes signal 331 in mannerwell-known in the art. More specifically, modem 303 includes ananalog-to-digital converter (ADC) to convert the received signal outputfrom directional coupler 331 into digital format. Once converted todigital format, the signal is demodulated by a demodulator and decodedby decoder to obtain the encoded data on the received wave. The decodeddata is then sent to a controller, which sends it to its destination(e.g., a computer system).

Modem 303 also includes an encoder that encodes data to be transmitted.The encoded data is modulated by a modulator and then converted toanalog by a digital-to-analog converter (DAC) (not shown) to produceanalog signal 332. Analog signal 332 is then filtered by a BUC (a blockupconverter) 304 and provided to one port of diplexer 305. In oneembodiment, BUC 304 is in an out-door unit (ODU). Diplexer 305 operatingin a manner well-known in the art provides the transmit signal 332 toASM 301 for transmission.

In one embodiment, to support its operations, modem 303 includes anintermediate frequency (IF) transceiver 310 to process transmit andreceive signals at an intermediate frequency, a digital basebandprocessor 311 to process down-converted digital signals to retrieve datafor a digital system, memory 312 stores parameters, data tables, andother information used by the modem to perform modulation, demodulationand its other functions, a clock management unit 313 to managingclocking of operations of modem 303, and a power management unit 314 tomanage power consumption of modem 303. These unit operate in a mannerwell-known in the art unless specified otherwise.

In operation, in one embodiment, as one satellite begins to leave thefield of view of the terminal, the antenna aperture of ASM 301 iscontrolled so that it changes from the single-beam configuration intotwo beams and begins setting up a connection with the next satellitewith the second beam. In one embodiment, the second beam is only forlocating and connecting with the next satellite and not transmittinglarge amounts of data, and thus the gain of the second beam with respectto the primary beam is lower, allowing for reduced, and potentiallyminimal, impact onto the data transmission rates of the satelliteterminal.

In one embodiment, two beams are generated simultaneously with a singleelectronically steered flat antenna in order to access a satellite, andthen a handoff of traffic from a first beam to a second beam happensseamlessly, whereas the first beam and the second beam are pointed atthe same satellite, yet are accessing satellite carriers on distinctfrequencies. An example of this is shown in FIG. 4.

Referring to FIG. 4, host processor 401 generates pointing and trackinginformation 400 and sends it to ASM 301 for one or two receive beams. Inone embodiment, pointing and tracking information 400 includes theta(e.g., Theta1), phi (e.g., Phi1), frequency (e.g., freq1, freq2), andsymbol rate (e.g., SR1) information. This may be in response to signalquality information or metrics, such as, for example, SINR values (e.g.,SINR1, SINR2) or Received Signal Strength Indicator (RSSI) (e.g., RSSI1,RSSI2) associated with received signals associated with received beams 1and 2. In one embodiment, this is in response to physical layersynchronization signals (e.g., PLsynch1, PLsynch2) that indicate thatthe antenna beam is tracking a satellite. In one embodiment, the signalquality information or metrics and sync signals are received from modem303.

Using beams 1 and 2, the antenna aperture of ASM 301 receives signalsfrom one or two satellites. The received signals are sent to diplexer305 and then to LNB 306, which operates as discussed above. From LNB306, the signals are sent to 2-way power divider 430, which divides thereceived signal into tracking receive signal (Rx1) 431 and trackingreceive signal (Rx2) 432. In one embodiment, tracking receive signal(Rx1) 431 and tracking receive signal (Rx2) 432 terminate at an RF tunerinside modem 303 where the frequency selection occurs. In this case,power divider 430 is a simple power splitter. In another embodiment,power divider 430 operates as a bandpass filter to filter the incomingsignal to produce tracking receive signal (Rx1) 431 and tracking receivesignal (Rx2) 432. These signals are sent to modem 303 and processed asdescribed above.

Although not shown in FIG. 4, in one embodiment, a second splitter/powerdivider is placed before LNB 306 and is included to split between Rx1and Rx2.

In one embodiment, a second beam is generated with an electronicallysteered flat antenna and pointed based on the estimate of the newsatellite location provided by two-line elements (TLE), which is a listof orbital elements of an Earth-orbiting object for a given point intime, and then that estimate of a second satellite location is improvedusing modem signal feedback for optimization.

In one embodiment, an unequal beam split is generated, thereby, with oneantenna producing two beams with different gains (e.g., gains differ byapproximately 10 dB for High-Throughput Satellites (HTS), etc.), suchthat the original beam maintains data communication and tracks a firstsatellite, while the second lower-gain beam is used to optimize the beampointing towards the new incoming satellite.

In one embodiment, the antenna used in the above embodiments can beduplex apertures, supporting simultaneous transmit and receivefunctions, rather than a receive-only aperture, thereby providing forhandoff of transmit traffic as well as handoff of receive traffic.

In one embodiment, the handoff of transmit traffic occurs for twodistinct satellites from satellites used for receive traffic, i.e., thetransmission satellites and reception satellites do not necessarily haveto be the same.

The techniques disclosed herein may be applied to, for example, but notlimited to, GEO (geostationary), MEO (medium earth orbit), LEO (lowearth orbit), any nonstationary and stationary satellite constellations,as well as multiple spacecraft with tracking capability implementedusing electronically steered antennas systems that do not require movingmechanical parts to steer a beam.

For instance, in one LEO constellation, satellites are in the field ofview of the ground terminal for short period of time, e.g., on the orderof 4 minutes, and every passing satellite is replaced by anotherincoming satellite, such that there is overlap for satelliteconnectivity. The LEO satellite locations as a function of time aretypically known via two-line elements, TLE, and are communicated to theground terminal during the satellite connectivity. As the moment of asatellite handoff approaches, the ground terminal creates a secondantenna beam and points that beam in the direction specified by the TLEfor the incoming satellite, and does so before the outgoing satellite isno longer in the field of view, thereby providing make-before-breakcapability. In one embodiment, the ground terminal is able to track anddeliver user traffic from a first beam pointed at a first LEO satellitewhile simultaneously acquiring a new incoming LEO satellite with asecond beam, after which it manages a seamless handoff of traffic fromthe first beam to the second beam and then turns off the first beam,thereby providing continuous service to its users.

Embodiments of the invention provide continuous satellite connectivity.In one embodiment, the purpose of the beam splitting is to reduce, andpotentially eliminate the amount of time the connectivity is interruptedbetween satellite hand-offs. Since these hand-offs will occur repeatedlyas LEO satellites orbit, any reduction in connectivity disruptionimproves the user experience with less drops in connectivity.

FIG. 5A is a timing diagram of one embodiment of a process in which onereceive beam is split to two receive beams. The original beam (Beam 1)501 is used for Forward Link data, aka FL, whereas the split beam, beam2, in the split beam period 502 is utilized to track the incoming LEOsatellite. The FL refers to the signal started from the Ground Network(GN) (aka HUB) and ending at the terminal. In one embodiment, the twobeams do not have equal antenna gain. In one embodiment, the secondbeam, beam 2, is given sufficient antenna gain so the terminal Rx modemcan use the split beam signal for acquiring the incoming satellite. Oncethe incoming satellite is acquired, then FL handoff takes place. In oneembodiment, FL data capacity is limited by the received signal strength(e.g., signal-to-noise ratio (SNR)) and determined by GN. During thebeam split period 502, the data capacity is lowered because the trafficbearing beam will have lower antenna gain than normal, shown ascompressed mode in FIG. 5A. The compressed mode stands for reducedmodulation and coding scheme (MODCOD) (e.g., MCS) due to splitting thebeam, i.e., reduced antenna gain, just long enough to track and connectto the incoming satellite. Once the split beam period 502 is complete,the traffic bearing beam (e.g., beam 2 going forward) can be returned tofull antenna gain.

In one embodiment, the techniques described herein also extend toreverse link, RL, connectivity, which would be established as soon as FLis handed off. In other words, although a FL handoff is discussed above,the RL handoff also occurs due to antenna duplex capabilities. FIG. 5Billustrates an example of a transmit (Tx) beam splitting and handoff andcorresponding timing diagram. Referring to FIG. 5B, the Tx beamsplitting does not necessarily occur for the same satellite or beam asfor receive (Rx) beam splitting. It could however be the very samesatellite or beam.

Examples of Antenna Embodiments

The techniques described above may be used with flat panel antennas.Embodiments of such flat panel antennas are disclosed. The flat panelantennas include one or more arrays of antenna elements on an antennaaperture. In one embodiment, the antenna elements comprise liquidcrystal cells. In one embodiment, the flat panel antenna is acylindrically fed antenna that includes matrix drive circuitry touniquely address and drive each of the antenna elements that are notplaced in rows and columns. In one embodiment, the elements are placedin rings.

In one embodiment, the antenna aperture having the one or more arrays ofantenna elements is comprised of multiple segments coupled together.When coupled together, the combination of the segments form closedconcentric rings of antenna elements. In one embodiment, the concentricrings are concentric with respect to the antenna feed.

Examples of Antenna Systems

In one embodiment, the flat panel antenna is part of a metamaterialantenna system. Embodiments of a metamaterial antenna system forcommunications satellite earth stations are described. In oneembodiment, the antenna system is a component or subsystem of asatellite earth station (ES) operating on a mobile platform (e.g.,aeronautical, maritime, land, etc.) that operates using either Ka-bandfrequencies or Ku-band frequencies for civil commercial satellitecommunications. Note that embodiments of the antenna system also can beused in earth stations that are not on mobile platforms (e.g., fixed ortransportable earth stations).

In one embodiment, the antenna system uses surface scatteringmetamaterial technology to form and steer transmit and receive beamsthrough separate antennas. In one embodiment, the antenna systems areanalog systems, in contrast to antenna systems that employ digitalsignal processing to electrically form and steer beams (such as phasedarray antennas).

In one embodiment, the antenna system is comprised of three functionalsubsystems: (1) a wave guiding structure consisting of a cylindricalwave feed architecture; (2) an array of wave scattering metamaterialunit cells that are part of antenna elements; and (3) a controlstructure to command formation of an adjustable radiation field (beam)from the metamaterial scattering elements using holographic principles.

Antenna Elements

FIG. 6 illustrates the schematic of one embodiment of a cylindricallyfed holographic radial aperture antenna. Referring to FIG. 6, theantenna aperture has one or more arrays 601 of antenna elements 603 thatare placed in concentric rings around an input feed 602 of thecylindrically fed antenna. In one embodiment, antenna elements 603 areradio frequency (RF) resonators that radiate RF energy. In oneembodiment, antenna elements 603 comprise both Rx and Tx irises that areinterleaved and distributed on the whole surface of the antennaaperture. Such Rx and Tx irises, or slots, may be in groups of three ormore sets where each set is for a separately and simultaneouslycontrolled band. Examples of such antenna elements with irises aredescribed in greater detail below. Note that the RF resonators describedherein may be used in antennas that do not include a cylindrical feed.

In one embodiment, the antenna includes a coaxial feed that is used toprovide a cylindrical wave feed via input feed 602. In one embodiment,the cylindrical wave feed architecture feeds the antenna from a centralpoint with an excitation that spreads outward in a cylindrical mannerfrom the feed point. That is, a cylindrically fed antenna creates anoutward travelling concentric feed wave. Even so, the shape of thecylindrical feed antenna around the cylindrical feed can be circular,square or any shape. In another embodiment, a cylindrically fed antennacreates an inward travelling feed wave. In such a case, the feed wavemost naturally comes from a circular structure.

In one embodiment, antenna elements 603 comprise irises and the apertureantenna of FIG. 6 is used to generate a main beam shaped by usingexcitation from a cylindrical feed wave for radiating irises throughtunable liquid crystal (LC) material. In one embodiment, the antenna canbe excited to radiate a horizontally or vertically polarized electricfield at desired scan angles.

In one embodiment, the antenna elements comprise a group of patchantennas. This group of patch antennas comprises an array of scatteringmetamaterial elements. In one embodiment, each scattering element in theantenna system is part of a unit cell that consists of a lowerconductor, a dielectric substrate and an upper conductor that embeds acomplementary electric inductive-capacitive resonator (“complementaryelectric LC” or “CELC”) that is etched in or deposited onto the upperconductor. As would be understood by those skilled in the art, LC in thecontext of CELC refers to inductance-capacitance, as opposed to liquidcrystal.

In one embodiment, a liquid crystal (LC) is disposed in the gap aroundthe scattering element. This LC is driven by the direct driveembodiments described above. In one embodiment, liquid crystal isencapsulated in each unit cell and separates the lower conductorassociated with a slot from an upper conductor associated with itspatch. Liquid crystal has a permittivity that is a function of theorientation of the molecules comprising the liquid crystal, and theorientation of the molecules (and thus the permittivity) can becontrolled by adjusting the bias voltage across the liquid crystal.Using this property, in one embodiment, the liquid crystal integrates anon/off switch for the transmission of energy from the guided wave to theCELC. When switched on, the CELC emits an electromagnetic wave like anelectrically small dipole antenna. Note that the teachings herein arenot limited to having a liquid crystal that operates in a binary fashionwith respect to energy transmission.

In one embodiment, the feed geometry of this antenna system allows theantenna elements to be positioned at forty-five degree (45°) angles tothe vector of the wave in the wave feed. Note that other positions maybe used (e.g., at 40° angles). This position of the elements enablescontrol of the free space wave received by or transmitted/radiated fromthe elements. In one embodiment, the antenna elements are arranged withan inter-element spacing that is less than a free-space wavelength ofthe operating frequency of the antenna. For example, if there are fourscattering elements per wavelength, the elements in the 30 GHz transmitantenna will be approximately 2.5 mm (i.e., ¼th the 10 mm free-spacewavelength of 30 GHz).

In one embodiment, the two sets of elements are perpendicular to eachother and simultaneously have equal amplitude excitation if controlledto the same tuning state. Rotating them+/−45 degrees relative to thefeed wave excitation achieves both desired features at once. Rotatingone set 0 degrees and the other 90 degrees would achieve theperpendicular goal, but not the equal amplitude excitation goal. Notethat 0 and 90 degrees may be used to achieve isolation when feeding thearray of antenna elements in a single structure from two sides.

The amount of radiated power from each unit cell is controlled byapplying a voltage to the patch (potential across the LC channel) usinga controller. Traces to each patch are used to provide the voltage tothe patch antenna. The voltage is used to tune or detune the capacitanceand thus the resonance frequency of individual elements to effectuatebeam forming. The voltage required is dependent on the liquid crystalmixture being used. The voltage tuning characteristic of liquid crystalmixtures is mainly described by a threshold voltage at which the liquidcrystal starts to be affected by the voltage and the saturation voltage,above which an increase of the voltage does not cause major tuning inliquid crystal. These two characteristic parameters can change fordifferent liquid crystal mixtures.

In one embodiment, as discussed above, a matrix drive is used to applyvoltage to the patches in order to drive each cell separately from allthe other cells without having a separate connection for each cell(direct drive). Because of the high density of elements, the matrixdrive is an efficient way to address each cell individually.

In one embodiment, the control structure for the antenna system has 2main components: the antenna array controller, which includes driveelectronics, for the antenna system, is below the wave scatteringstructure (of surface scattering antenna elements such as describedherein), while the matrix drive switching array is interspersedthroughout the radiating RF array in such a way as to not interfere withthe radiation. In one embodiment, the drive electronics for the antennasystem comprise commercial off-the-shelf LCD controls used in commercialtelevision appliances that adjust the bias voltage for each scatteringelement by adjusting the amplitude or duty cycle of an AC bias signal tothat element.

In one embodiment, the antenna array controller also contains amicroprocessor executing the software. The control structure may alsoincorporate sensors (e.g., a GPS receiver, a three-axis compass, a3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, etc.) to providelocation and orientation information to the processor. The location andorientation information may be provided to the processor by othersystems in the earth station and/or may not be part of the antennasystem.

More specifically, the antenna array controller controls which elementsare turned off and those elements turned on and at which phase andamplitude level at the frequency of operation. The elements areselectively detuned for frequency operation by voltage application.

For transmission, a controller supplies an array of voltage signals tothe RF patches to create a modulation, or control pattern. The controlpattern causes the elements to be turned to different states. In oneembodiment, multistate control is used in which various elements areturned on and off to varying levels, further approximating a sinusoidalcontrol pattern, as opposed to a square wave (i.e., a sinusoid grayshade modulation pattern). In one embodiment, some elements radiate morestrongly than others, rather than some elements radiate and some do not.Variable radiation is achieved by applying specific voltage levels,which adjusts the liquid crystal permittivity to varying amounts,thereby detuning elements variably and causing some elements to radiatemore than others.

The generation of a focused beam by the metamaterial array of elementscan be explained by the phenomenon of constructive and destructiveinterference. Individual electromagnetic waves sum up (constructiveinterference) if they have the same phase when they meet in free spaceand waves cancel each other (destructive interference) if they are inopposite phase when they meet in free space. If the slots in a slottedantenna are positioned so that each successive slot is positioned at adifferent distance from the excitation point of the guided wave, thescattered wave from that element will have a different phase than thescattered wave of the previous slot. If the slots are spaced one quarterof a guided wavelength apart, each slot will scatter a wave with a onefourth phase delay from the previous slot.

Using the array, the number of patterns of constructive and destructiveinterference that can be produced can be increased so that beams can bepointed theoretically in any direction plus or minus ninety degrees(90°) from the bore sight of the antenna array, using the principles ofholography. Thus, by controlling which metamaterial unit cells areturned on or off (i.e., by changing the pattern of which cells areturned on and which cells are turned off), a different pattern ofconstructive and destructive interference can be produced, and theantenna can change the direction of the main beam. The time required toturn the unit cells on and off dictates the speed at which the beam canbe switched from one location to another location.

In one embodiment, the antenna system produces one steerable beam forthe uplink antenna and one steerable beam for the downlink antenna. Inone embodiment, the antenna system uses metamaterial technology toreceive beams and to decode signals from the satellite and to formtransmit beams that are directed toward the satellite. In oneembodiment, the antenna systems are analog systems, in contrast toantenna systems that employ digital signal processing to electricallyform and steer beams (such as phased array antennas). In one embodiment,the antenna system is considered a “surface” antenna that is planar andrelatively low profile, especially when compared to conventionalsatellite dish receivers.

FIG. 7 illustrates a perspective view of one row of antenna elementsthat includes a ground plane and a reconfigurable resonator layer.Reconfigurable resonator layer 1230 includes an array of tunable slots1210. The array of tunable slots 1210 can be configured to point theantenna in a desired direction. Each of the tunable slots can betuned/adjusted by varying a voltage across the liquid crystal.

Control module, or controller, 1280 is coupled to reconfigurableresonator layer 1230 to modulate the array of tunable slots 1210 byvarying the voltage across the liquid crystal in FIG. 8A. Control module1280 may include a Field Programmable Gate Array (“FPGA”), amicroprocessor, a controller, System-on-a-Chip (SoC), or otherprocessing logic. In one embodiment, control module 1280 includes logiccircuitry (e.g., multiplexer) to drive the array of tunable slots 1210.In one embodiment, control module 1280 receives data that includesspecifications for a holographic diffraction pattern to be driven ontothe array of tunable slots 1210. The holographic diffraction patternsmay be generated in response to a spatial relationship between theantenna and a satellite so that the holographic diffraction patternsteers the downlink beams (and uplink beam if the antenna systemperforms transmit) in the appropriate direction for communication.Although not drawn in each figure, a control module similar to controlmodule 1280 may drive each array of tunable slots described in thefigures of the disclosure.

Radio Frequency (“RF”) holography is also possible using analogoustechniques where a desired RF beam can be generated when an RF referencebeam encounters an RF holographic diffraction pattern. In the case ofsatellite communications, the reference beam is in the form of a feedwave, such as feed wave 1205 (approximately 20 GHz in some embodiments).To transform a feed wave into a radiated beam (either for transmittingor receiving purposes), an interference pattern is calculated betweenthe desired RF beam (the object beam) and the feed wave (the referencebeam). The interference pattern is driven onto the array of tunableslots 1210 as a diffraction pattern so that the feed wave is “steered”into the desired RF beam (having the desired shape and direction). Inother words, the feed wave encountering the holographic diffractionpattern “reconstructs” the object beam, which is formed according todesign requirements of the communication system. The holographicdiffraction pattern contains the excitation of each element and iscalculated by w_(hologram)=w*_(in)w_(out), with w_(in) as the waveequation in the waveguide and w_(out) the wave equation on the outgoingwave.

FIG. 8A illustrates one embodiment of a tunable resonator/slot 1210.Tunable slot 1210 includes an iris/slot 1212, a radiating patch 1211,and liquid crystal 1213 disposed between iris 1212 and patch 1211. Inone embodiment, radiating patch 1211 is co-located with iris 1212.

FIG. 8B illustrates a cross section view of one embodiment of a physicalantenna aperture. The antenna aperture includes ground plane 1245, and ametal layer 1236 within iris layer 1233, which is included inreconfigurable resonator layer 1230. In one embodiment, the antennaaperture of FIG. 8B includes a plurality of tunable resonator/slots 1210of FIG. 8A. Iris/slot 1212 is defined by openings in metal layer 1236. Afeed wave, such as feed wave 1205 of FIG. 8A, may have a microwavefrequency compatible with satellite communication channels. The feedwave propagates between ground plane 1245 and resonator layer 1230.

Reconfigurable resonator layer 1230 also includes gasket layer 1232 andpatch layer 1231. Gasket layer 1232 is disposed between patch layer 1231and iris layer 1233. Note that in one embodiment, a spacer could replacegasket layer 1232. In one embodiment, iris layer 1233 is a printedcircuit board (“PCB”) that includes a copper layer as metal layer 1236.In one embodiment, iris layer 1233 is glass. Iris layer 1233 may beother types of substrates.

Openings may be etched in the copper layer to form slots 1212. In oneembodiment, iris layer 1233 is conductively coupled by a conductivebonding layer to another structure (e.g., a waveguide) in FIG. 8B. Notethat in an embodiment the iris layer is not conductively coupled by aconductive bonding layer and is instead interfaced with a non-conductingbonding layer.

Patch layer 1231 may also be a PCB that includes metal as radiatingpatches 1211. In one embodiment, gasket layer 1232 includes spacers 1239that provide a mechanical standoff to define the dimension between metallayer 1236 and patch 1211. In one embodiment, the spacers are 75microns, but other sizes may be used (e.g., 3-200 mm). As mentionedabove, in one embodiment, the antenna aperture of FIG. 8B includesmultiple tunable resonator/slots, such as tunable resonator/slot 1210includes patch 1211, liquid crystal 1213, and iris 1212 of FIG. 8A. Thechamber for liquid crystal 1213 is defined by spacers 1239, iris layer1233 and metal layer 1236. When the chamber is filled with liquidcrystal, patch layer 1231 can be laminated onto spacers 1239 to sealliquid crystal within resonator layer 1230.

A voltage between patch layer 1231 and iris layer 1233 can be modulatedto tune the liquid crystal in the gap between the patch and the slots(e.g., tunable resonator/slot 1210). Adjusting the voltage across liquidcrystal 1213 varies the capacitance of a slot (e.g., tunableresonator/slot 1210). Accordingly, the reactance of a slot (e.g.,tunable resonator/slot 1210) can be varied by changing the capacitance.Resonant frequency of slot 1210 also changes according to the equation

$f = \frac{1}{2\pi\sqrt{LC}}$where f is the resonant frequency of slot 1210 and L and C are theinductance and capacitance of slot 1210, respectively. The resonantfrequency of slot 1210 affects the energy radiated from feed wave 1205propagating through the waveguide. As an example, if feed wave 1205 is20 GHz, the resonant frequency of a slot 1210 may be adjusted (byvarying the capacitance) to 17 GHz so that the slot 1210 couplessubstantially no energy from feed wave 1205. Or, the resonant frequencyof a slot 1210 may be adjusted to 20 GHz so that the slot 1210 couplesenergy from feed wave 1205 and radiates that energy into free space.Although the examples given are binary (fully radiating or not radiatingat all), full gray scale control of the reactance, and therefore theresonant frequency of slot 1210 is possible with voltage variance over amulti-valued range. Hence, the energy radiated from each slot 1210 canbe finely controlled so that detailed holographic diffraction patternscan be formed by the array of tunable slots.

In one embodiment, tunable slots in a row are spaced from each other byλ/5. Other spacings may be used. In one embodiment, each tunable slot ina row is spaced from the closest tunable slot in an adjacent row by λ/2,and, thus, commonly oriented tunable slots in different rows are spacedby λ/4, though other spacings are possible (e.g., λ/5, λ/6.3). Inanother embodiment, each tunable slot in a row is spaced from theclosest tunable slot in an adjacent row by λ/3.

Embodiments use reconfigurable metamaterial technology, such asdescribed in U.S. patent application Ser. No. 14/550,178, entitled“Dynamic Polarization and Coupling Control from a SteerableCylindrically Fed Holographic Antenna”, filed Nov. 21, 2014 and U.S.patent application Ser. No. 14/610,502, entitled “Ridged Waveguide FeedStructures for Reconfigurable Antenna”, filed Jan. 30, 2015.

FIGS. 9A-D illustrate one embodiment of the different layers forcreating the slotted array. The antenna array includes antenna elementsthat are positioned in rings, such as the example rings shown in FIG.1A. Note that in this example the antenna array has two different typesof antenna elements that are used for two different types of frequencybands.

FIG. 9A illustrates a portion of the first iris board layer withlocations corresponding to the slots. Referring to FIG. 9A, the circlesare open areas/slots in the metallization in the bottom side of the irissubstrate, and are for controlling the coupling of elements to the feed(the feed wave). Note that this layer is an optional layer and is notused in all designs. FIG. 9B illustrates a portion of the second irisboard layer containing slots. FIG. 9C illustrates patches over a portionof the second iris board layer. FIG. 9D illustrates a top view of aportion of the slotted array.

FIG. 10 illustrates a side view of one embodiment of a cylindrically fedantenna structure. The antenna produces an inwardly travelling waveusing a double layer feed structure (i.e., two layers of a feedstructure). In one embodiment, the antenna includes a circular outershape, though this is not required. That is, non-circular inwardtravelling structures can be used. In one embodiment, the antennastructure in FIG. 10 includes a coaxial feed, such as, for example,described in U.S. Publication No. 2015/0236412, entitled “DynamicPolarization and Coupling Control from a Steerable Cylindrically FedHolographic Antenna”, filed on Nov. 21, 2014.

Referring to FIG. 10, a coaxial pin 1601 is used to excite the field onthe lower level of the antenna. In one embodiment, coaxial pin 1601 is a50Ωcoax pin that is readily available. Coaxial pin 1601 is coupled(e.g., bolted) to the bottom of the antenna structure, which isconducting ground plane 1602.

Separate from conducting ground plane 1602 is interstitial conductor1603, which is an internal conductor. In one embodiment, conductingground plane 1602 and interstitial conductor 1603 are parallel to eachother. In one embodiment, the distance between ground plane 1602 andinterstitial conductor 1603 is 0.1-0.15″. In another embodiment, thisdistance may be λ/2, where λ is the wavelength of the travelling wave atthe frequency of operation.

Ground plane 1602 is separated from interstitial conductor 1603 via aspacer 1604. In one embodiment, spacer 1604 is a foam or air-likespacer. In one embodiment, spacer 1604 comprises a plastic spacer.

On top of interstitial conductor 1603 is dielectric layer 1605. In oneembodiment, dielectric layer 1605 is plastic. The purpose of dielectriclayer 1605 is to slow the travelling wave relative to free spacevelocity. In one embodiment, dielectric layer 1605 slows the travellingwave by 30% relative to free space. In one embodiment, the range ofindices of refraction that are suitable for beam forming are 1.2-1.8,where free space has by definition an index of refraction equal to 1.Other dielectric spacer materials, such as, for example, plastic, may beused to achieve this effect. Note that materials other than plastic maybe used as long as they achieve the desired wave slowing effect.Alternatively, a material with distributed structures may be used asdielectric 1605, such as periodic sub-wavelength metallic structuresthat can be machined or lithographically defined, for example.

An RF-array 1606 is on top of dielectric 1605. In one embodiment, thedistance between interstitial conductor 1603 and RF-array 1606 is0.1-0.15″. In another embodiment, this distance may be λ_(eff)/2, whereλ_(eff) is the effective wavelength in the medium at the designfrequency.

The antenna includes sides 1607 and 1608. Sides 1607 and 1608 are angledto cause a travelling wave feed from coax pin 1601 to be propagated fromthe area below interstitial conductor 1603 (the spacer layer) to thearea above interstitial conductor 1603 (the dielectric layer) viareflection. In one embodiment, the angle of sides 1607 and 1608 are at45° angles. In an alternative embodiment, sides 1607 and 1608 could bereplaced with a continuous radius to achieve the reflection. While FIG.10 shows angled sides that have angle of 45 degrees, other angles thataccomplish signal transmission from lower level feed to upper level feedmay be used. That is, given that the effective wavelength in the lowerfeed will generally be different than in the upper feed, some deviationfrom the ideal 45° angles could be used to aid transmission from thelower to the upper feed level. For example, in another embodiment, the45° angles are replaced with a single step. The steps on one end of theantenna go around the dielectric layer, interstitial the conductor, andthe spacer layer. The same two steps are at the other ends of theselayers.

In operation, when a feed wave is fed in from coaxial pin 1601, the wavetravels outward concentrically oriented from coaxial pin 1601 in thearea between ground plane 1602 and interstitial conductor 1603. Theconcentrically outgoing waves are reflected by sides 1607 and 1608 andtravel inwardly in the area between interstitial conductor 1603 and RFarray 1606. The reflection from the edge of the circular perimetercauses the wave to remain in phase (i.e., it is an in-phase reflection).The travelling wave is slowed by dielectric layer 1605. At this point,the travelling wave starts interacting and exciting with elements in RFarray 1606 to obtain the desired scattering.

To terminate the travelling wave, a termination 1609 is included in theantenna at the geometric center of the antenna. In one embodiment,termination 1609 comprises a pin termination (e.g., a 50Ω pin). Inanother embodiment, termination 1609 comprises an RF absorber thatterminates unused energy to prevent reflections of that unused energyback through the feed structure of the antenna. These could be used atthe top of RF array 1606.

FIG. 11 illustrates another embodiment of the antenna system with anoutgoing wave. Referring to FIG. 11, two ground planes 1610 and 1611 aresubstantially parallel to each other with a dielectric layer 1612 (e.g.,a plastic layer, etc.) in between ground planes. RF absorbers 1619(e.g., resistors) couple the two ground planes 1610 and 1611 together. Acoaxial pin 1615 (e.g., 50Ω) feeds the antenna. An RF array 1616 is ontop of dielectric layer 1612 and ground plane 1611.

In operation, a feed wave is fed through coaxial pin 1615 and travelsconcentrically outward and interacts with the elements of RF array 1616.

The cylindrical feed in both the antennas of FIGS. 10 and 11 improvesthe service angle of the antenna. Instead of a service angle of plus orminus forty-five degrees azimuth (±45° Az) and plus or minus twenty-fivedegrees elevation (±25° El), in one embodiment, the antenna system has aservice angle of seventy-five degrees (75°) from the bore sight in alldirections. As with any beam forming antenna comprised of manyindividual radiators, the overall antenna gain is dependent on the gainof the constituent elements, which themselves are angle-dependent. Whenusing common radiating elements, the overall antenna gain typicallydecreases as the beam is pointed further off bore sight. At 75 degreesoff bore sight, significant gain degradation of about 6 dB is expected.

Embodiments of the antenna having a cylindrical feed solve one or moreproblems. These include dramatically simplifying the feed structurecompared to antennas fed with a corporate divider network and thereforereducing total required antenna and antenna feed volume; decreasingsensitivity to manufacturing and control errors by maintaining high beamperformance with coarser controls (extending all the way to simplebinary control); giving a more advantageous side lobe pattern comparedto rectilinear feeds because the cylindrically oriented feed wavesresult in spatially diverse side lobes in the far field; and allowingpolarization to be dynamic, including allowing left-hand circular,right-hand circular, and linear polarizations, while not requiring apolarizer.

Array of Wave Scattering Elements

RF array 1606 of FIG. 10 and RF array 1616 of FIG. 11 include a wavescattering subsystem that includes a group of patch antennas (i.e.,scatterers) that act as radiators. This group of patch antennascomprises an array of scattering metamaterial elements.

In one embodiment, each scattering element in the antenna system is partof a unit cell that consists of a lower conductor, a dielectricsubstrate and an upper conductor that embeds a complementary electricinductive-capacitive resonator (“complementary electric LC” or “CELL”)that is etched in or deposited onto the upper conductor.

In one embodiment, a liquid crystal (LC) is injected in the gap aroundthe scattering element. Liquid crystal is encapsulated in each unit celland separates the lower conductor associated with a slot from an upperconductor associated with its patch. Liquid crystal has a permittivitythat is a function of the orientation of the molecules comprising theliquid crystal, and the orientation of the molecules (and thus thepermittivity) can be controlled by adjusting the bias voltage across theliquid crystal. Using this property, the liquid crystal acts as anon/off switch for the transmission of energy from the guided wave to theCELC. When switched on, the CELC emits an electromagnetic wave like anelectrically small dipole antenna.

Controlling the thickness of the LC increases the beam switching speed.A fifty percent (50%) reduction in the gap between the lower and theupper conductor (the thickness of the liquid crystal) results in afourfold increase in speed. In another embodiment, the thickness of theliquid crystal results in a beam switching speed of approximatelyfourteen milliseconds (14 ms). In one embodiment, the LC is doped in amanner well-known in the art to improve responsiveness so that a sevenmillisecond (7 ms) requirement can be met.

The CELC element is responsive to a magnetic field that is appliedparallel to the plane of the CELC element and perpendicular to the CELCgap complement. When a voltage is applied to the liquid crystal in themetamaterial scattering unit cell, the magnetic field component of theguided wave induces a magnetic excitation of the CELC, which, in turn,produces an electromagnetic wave in the same frequency as the guidedwave.

The phase of the electromagnetic wave generated by a single CELC can beselected by the position of the CELC on the vector of the guided wave.Each cell generates a wave in phase with the guided wave parallel to theCELC. Because the CELCs are smaller than the wave length, the outputwave has the same phase as the phase of the guided wave as it passesbeneath the CELC.

In one embodiment, the cylindrical feed geometry of this antenna systemallows the CELC elements to be positioned at forty-five degree (45°)angles to the vector of the wave in the wave feed. This position of theelements enables control of the polarization of the free space wavegenerated from or received by the elements. In one embodiment, the CELCsare arranged with an inter-element spacing that is less than afree-space wavelength of the operating frequency of the antenna. Forexample, if there are four scattering elements per wavelength, theelements in the 30 GHz transmit antenna will be approximately 2.5 mm(i.e., ¼th the 10 mm free-space wavelength of 30 GHz).

In one embodiment, the CELCs are implemented with patch antennas thatinclude a patch co-located over a slot with liquid crystal between thetwo. In this respect, the metamaterial antenna acts like a slotted(scattering) wave guide. With a slotted wave guide, the phase of theoutput wave depends on the location of the slot in relation to theguided wave.

Cell Placement

In one embodiment, the antenna elements are placed on the cylindricalfeed antenna aperture in a way that allows for a systematic matrix drivecircuit. The placement of the cells includes placement of thetransistors for the matrix drive. FIG. 12 illustrates one embodiment ofthe placement of matrix drive circuitry with respect to antennaelements. Referring to FIG. 12, row controller 1701 is coupled totransistors 1711 and 1712, via row select signals Row1 and Row2,respectively, and column controller 1702 is coupled to transistors 1711and 1712 via column select signal Column1. Transistor 1711 is alsocoupled to antenna element 1721 via connection to patch 1731, whiletransistor 1712 is coupled to antenna element 1722 via connection topatch 1732.

In an initial approach to realize matrix drive circuitry on thecylindrical feed antenna with unit cells placed in a non-regular grid,two steps are performed. In the first step, the cells are placed onconcentric rings and each of the cells is connected to a transistor thatis placed beside the cell and acts as a switch to drive each cellseparately. In the second step, the matrix drive circuitry is built inorder to connect every transistor with a unique address as the matrixdrive approach requires. Because the matrix drive circuit is built byrow and column traces (similar to LCDs) but the cells are placed onrings, there is no systematic way to assign a unique address to eachtransistor. This mapping problem results in very complex circuitry tocover all the transistors and leads to a significant increase in thenumber of physical traces to accomplish the routing. Because of the highdensity of cells, those traces disturb the RF performance of the antennadue to coupling effect. Also, due to the complexity of traces and highpacking density, the routing of the traces cannot be accomplished bycommercially available layout tools.

In one embodiment, the matrix drive circuitry is predefined before thecells and transistors are placed. This ensures a minimum number oftraces that are necessary to drive all the cells, each with a uniqueaddress. This strategy reduces the complexity of the drive circuitry andsimplifies the routing, which subsequently improves the RF performanceof the antenna.

More specifically, in one approach, in the first step, the cells areplaced on a regular rectangular grid composed of rows and columns thatdescribe the unique address of each cell. In the second step, the cellsare grouped and transformed to concentric circles while maintainingtheir address and connection to the rows and columns as defined in thefirst step. A goal of this transformation is not only to put the cellson rings but also to keep the distance between cells and the distancebetween rings constant over the entire aperture. In order to accomplishthis goal, there are several ways to group the cells.

In one embodiment, a TFT package is used to enable placement and uniqueaddressing in the matrix drive. FIG. 13 illustrates one embodiment of aTFT package. Referring to FIG. 13, a TFT and a hold capacitor 1803 isshown with input and output ports. There are two input ports connectedto traces 1801 and two output ports connected to traces 1802 to connectthe TFTs together using the rows and columns. In one embodiment, the rowand column traces cross in 90° angles to reduce, and potentiallyminimize, the coupling between the row and column traces. In oneembodiment, the row and column traces are on different layers.

An Example of a Full Duplex Communication System

In another embodiment, the combined antenna apertures are used in a fullduplex communication system. FIG. 14 is a block diagram of an embodimentof a communication system having simultaneous transmit and receivepaths. While only one transmit path and one receive path are shown, thecommunication system may include more than one transmit path and/or morethan one receive path.

Referring to FIG. 14, antenna 1401 includes two spatially interleavedantenna arrays operable independently to transmit and receivesimultaneously at different frequencies as described above. In oneembodiment, antenna 1401 is coupled to diplexer 1445. The coupling maybe by one or more feeding networks. In one embodiment, in the case of aradial feed antenna, diplexer 1445 combines the two signals and theconnection between antenna 1401 and diplexer 1445 is a single broad-bandfeeding network that can carry both frequencies.

Diplexer 1445 is coupled to a low noise block down converter (LNBs)1427, which performs a noise filtering function and a down conversionand amplification function in a manner well-known in the art. In oneembodiment, LNB 1427 is in an out-door unit (ODU). In anotherembodiment, LNB 1427 is integrated into the antenna apparatus. LNB 1427is coupled to a modem 1460, which is coupled to computing system 1440(e.g., a computer system, modem, etc.).

Modem 1460 includes an analog-to-digital converter (ADC) 1422, which iscoupled to LNB 1427, to convert the received signal output from diplexer1445 into digital format. Once converted to digital format, the signalis demodulated by demodulator 1423 and decoded by decoder 1424 to obtainthe encoded data on the received wave. The decoded data is then sent tocontroller 1425, which sends it to computing system 1440.

Modem 1460 also includes an encoder 1430 that encodes data to betransmitted from computing system 1440. The encoded data is modulated bymodulator 1431 and then converted to analog by digital-to-analogconverter (DAC) 1432. The analog signal is then filtered by a BUC(up-convert and high pass amplifier) 1433 and provided to one port ofdiplexer 1445. In one embodiment, BUC 1433 is in an out-door unit (ODU).

Diplexer 1445 operating in a manner well-known in the art provides thetransmit signal to antenna 1401 for transmission.

Controller 1450 controls antenna 1401, including the two arrays ofantenna elements on the single combined physical aperture.

The communication system would be modified to include thecombiner/arbiter described above. In such a case, the combiner/arbiterafter the modem but before the BUC and LNB.

Note that the full duplex communication system shown in FIG. 14 has anumber of applications, including but not limited to, internetcommunication, vehicle communication (including software updating), etc.

There is a number of example embodiments described herein.

Example 1 is a method comprising generating a first beam with a singleelectronically steered flat-panel antenna to track a first satellite;generating a second beam with the single electronically steeredflat-panel antenna to track a second satellite simultaneously whilegenerating the first beam to track the first satellite; and handing offtraffic from the first satellite to the second satellite.

Example 2 is the method of example 1 that may optionally include thathanding off traffic is performed seamlessly such that connectivity ismaintained throughout the transition from the first satellite to thesecond satellite.

Example 3 is the method of example 1 that may optionally include priorto generating the second beam to track the second satellite, generatingthe second beam to acquire a signal from the second satellite whilegenerating the first beam.

Example 4 is the method of example 3 that may optionally includegenerating first and second patterns to apply to first and second setsof radio-frequency (RF) radiating antenna elements, respectively, on anantenna aperture of the electronically steered flat-panel antenna togenerate the first and second beams, respectively, to point at carrierfrequencies that differ in frequency, wherein the RF radiating antennaelements of the first and second sets are different.

Example 5 is the method of example 4 that may optionally include thatthe first and second sets of RF radiating antenna elements have adifferent number of RF radiating antenna elements.

Example 6 is the method of example 4 that may optionally include that RFradiating antenna elements of the first and second sets of RF radiatingantenna elements are arbitrarily distributed on the antenna aperture.

Example 7 is the method of example 4 that may optionally include thatthe first and second sets of RF radiating antenna elements are in ringsaround a central feed for a wave, and further wherein each ring of thefirst set of RF radiating antenna elements is between rings of RFradiating antenna elements in the second set of RF radiating antennaelements.

Example 8 is the method of example 4 that may optionally include thatthe first and second sets of RF radiating antenna elements are in ringsaround a central feed for a wave, with the first set of RF radiatingantenna elements being in rings closest to the central feed incomparison to rings of the second set of RF radiating antenna elements.

Example 9 is the method of example 3 that may optionally include thatthe second beam is pointed to a predicted location of the secondsatellite.

Example 10 is the method of example 9 that may optionally include thatthe predicted location is based on commanded two-line elements (TLE).

Example 11 is the method of example 3 that may optionally include thatgenerating the first and second beams have different antenna gains,wherein gain for the second beam is lower than gain for the first beamwhen the second beam is used for acquiring the signal from the secondsatellite.

Example 12 is the method of example 3 that may optionally include thatthe second beam is wider than the first beam when used for acquiring thesignal from the second satellite.

Example 13 is the method of example 1 that may optionally include priorto generating the first beam to track the first satellite, operating theelectronically steered flat-panel antenna in a single-beam configurationin which the electronically steered flat-panel antenna is generating asingle beam, including generating a third beam to track the secondsatellite using a first set of RF radiating antenna elements on anantenna aperture of the electronically steered flat-panel antenna, thefirst set of RF radiating antenna elements including RF radiatingelements of a second set of RF radiating elements on the antennaaperture for generating the first beam and RF radiating elements of athird set of RF radiating elements on the antenna aperture forgenerating the second beam; and determining to switch the electronicallysteered flat-panel antenna to a two-beam configuration in which theelectronically steered flat-panel antenna is generating the first andsecond beams.

Example 14 is the method of example 13 that may optionally include thatthe first set of RF radiating antenna elements includes the second andthird set of RF radiating elements.

Example 15 is an antenna for use in satellite communication, the antennacomprising: an electronically steered flat-panel antenna aperture with aplurality of electronically controlled radio frequency (RF) radiatingantenna elements; and one or more processors coupled to the antennaaperture to control the antenna aperture to generate a first beam withthe antenna aperture to track a first satellite, to generate a secondbeam with the antenna aperture to track a second satellitesimultaneously while generating the first beam to track the firstsatellite, and to hand off traffic from the first satellite to thesecond satellite.

Example 16 is the antenna of example 15 that may optionally include thatthe one or more processors are operable to hand off traffic seamlesslybetween the first and second satellites such that connectivity ismaintained throughout the transition from the first satellite to thesecond satellite.

Example 17 is the antenna of example 15 that may optionally include,prior to generating the second beam to track the second satellite, theone or more processors control the antenna aperture to generate thesecond beam to acquire a signal from the second satellite whilegenerating the first beam.

Example 18 is the antenna of example 17 that may optionally include thatthe one or more processors are operable to generate first and secondpatterns to apply to first and second sets of first and second sets ofradio-frequency (RF) radiating antenna elements, respectively, of theantenna aperture to generate the first and second beams, respectively,to point at carriers frequencies that differ in frequency, wherein theRF radiating antenna elements of the first and second sets aredifferent.

Example 19 is the antenna of example 18 that may optionally include thatthe first and second sets of RF radiating antenna elements have adifferent number of RF radiating antenna elements.

Example 20 is the antenna of example 18 that may optionally include thatthe first and second sets of RF radiating antenna elements are in ringsaround a central feed for a wave, and further wherein each ring of thefirst set of RF radiating antenna elements is between rings of RFradiating antenna elements in the second set of RF radiating antennaelements.

Example 21 is the antenna of example 18 that may optionally include thatthe first and second sets of RF radiating antenna elements are in ringsaround a central feed for a wave, with the first set of RF radiatingantenna elements being in rings closest to the central feed incomparison to rings of the second set of RF radiating antenna elements.

Example 22 is the antenna of example 15 that may optionally include thatthe second beam is pointed to a predicted location of the secondsatellite.

Example 23 is the antenna of example 22 that may optionally include thatthe predicted location is based on commanded two-line elements (TLE).

Example 24 is the antenna of example 15 that may optionally include thatthe first and second beams have different antenna gains, wherein gainfor the second beam is lower than gain for the first beam when thesecond beam is used for acquiring the signal from the second satellite.

Example 25 is the antenna of example 15 that may optionally include thatthe second beam is wider than the first beam when used for acquiring asignal from the second satellite.

Some portions of the detailed descriptions above are presented in termsof algorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the following discussion,it is appreciated that throughout the description, discussions utilizingterms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

The present invention also relates to apparatus for performing theoperations herein. This apparatus may be specially constructed for therequired purposes, or it may comprise a general-purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a computerreadable storage medium, such as, but is not limited to, any type ofdisk including floppy disks, optical disks, CD-ROMs, andmagnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any typeof media suitable for storing electronic instructions, and each coupledto a computer system bus.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.In addition, the present invention is not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the invention as described herein.

A machine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes read onlymemory (“ROM”); random access memory (“RAM”); magnetic disk storagemedia; optical storage media; flash memory devices; etc.

Whereas many alterations and modifications of the present invention willno doubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that anyparticular embodiment shown and described by way of illustration is inno way intended to be considered limiting. Therefore, references todetails of various embodiments are not intended to limit the scope ofthe claims which in themselves recite only those features regarded asessential to the invention.

We claim:
 1. A method for use in satellite communication, the methodcomprising: generating a first beam with a single electronically steeredflat-panel antenna to track a first satellite; generating a second beamwith the single electronically steered flat-panel antenna to acquire asecond satellite simultaneously while generating the first beam to trackthe first satellite, wherein the first and second beams have differentantenna gains when the second beam is to acquire the second satelliteand the first beam is to track the first satellite; generating thesecond beam with the single electronically steered flat-panel antenna totrack the second satellite simultaneously while generating the firstbeam to track the first satellite, direction of the first and secondbeams being electronically controlled by the single electronicallysteered flat-panel antenna that electronically scans in multipledimensions; and handing off traffic from the first satellite to thesecond satellite.
 2. The method of claim 1 wherein gain for the secondbeam is lower than gain for the first beam when the second beam is usedfor acquiring the signal from the second satellite.
 3. The method ofclaim 1 wherein the second beam is wider than the first beam when usedfor acquiring the signal from the second satellite.
 4. The method ofclaim 1 wherein handing off traffic is performed seamlessly such thatconnectivity is maintained throughout the transition from the firstsatellite to the second satellite.
 5. The method of claim 1 furthercomprising generating first and second patterns to apply to first andsecond sets of radio-frequency (RF) radiating antenna elements,respectively, on an antenna aperture of the electronically steeredflat-panel antenna to generate the first and second beams, respectively,to point at carrier frequencies that differ in frequency, wherein the RFradiating antenna elements of the first and second sets are different.6. The method of claim 5 wherein the first and second sets of RFradiating antenna elements have a different number of RF radiatingantenna elements.
 7. The method of claim 5 wherein RF radiating antennaelements of the first and second sets of RF radiating antenna elementsare arbitrarily distributed on the antenna aperture.
 8. The method ofclaim 1 wherein the second beam is pointed to a predicted location ofthe second satellite.
 9. The method of claim 8 wherein the predictedlocation is based on commanded two-line elements (TLE).
 10. The methodof claim 1 further comprising: prior to generating the first beam totrack the first satellite, operating the electronically steeredflat-panel antenna in a single-beam configuration in which theelectronically steered flat-panel antenna is generating a single beam,including generating a third beam to track the second satellite using afirst set of RF radiating antenna elements on an antenna aperture of theelectronically steered flat-panel antenna, the first set of RF radiatingantenna elements including RF radiating elements of a second set of RFradiating elements on the antenna aperture for generating the first beamand RF radiating elements of a third set of RF radiating elements on theantenna aperture for generating the second beam; and determining toswitch the electronically steered flat-panel antenna to a two-beamconfiguration in which the electronically steered flat-panel antenna isgenerating the first and second beams.
 11. The method of claim 10wherein the first set of RF radiating antenna elements includes thesecond and third set of RF radiating elements.
 12. An antenna for use insatellite communication, the antenna comprising: an electronicallysteered flat-panel antenna aperture with a plurality of electronicallycontrolled radio frequency (RF) radiating antenna elements; and one ormore processors coupled to the antenna aperture to control the antennaaperture to generate a first beam with a single electronically steeredflat-panel antenna to track a first satellite; generate a second beamwith the single electronically steered flat-panel antenna to acquire asecond satellite simultaneously while generating the first beam to trackthe first satellite, wherein the first and second beams have differentantenna gains when the second beam is to acquire the second satelliteand the first beam is to track the first satellite; generate the secondbeam with the single electronically steered flat-panel antenna to trackthe second satellite simultaneously while generating the first beam totrack the first satellite, where direction of the first and second beamsis being electronically controlled by the single electronically steeredflat-panel antenna that electronically scans in multiple dimensions; andhand off traffic from the first satellite to the second satellite. 13.The antenna of claim 12 wherein gain for the second beam is lower thangain for the first beam when the second beam is used for acquiring thesignal from the second satellite.
 14. The antenna of claim 12 whereinthe second beam is wider than the first beam when used for acquiring thesignal from the second satellite.
 15. The antenna of claim 12 whereinhanding off traffic is performed seamlessly such that connectivity ismaintained throughout the transition from the first satellite to thesecond satellite.
 16. The antenna of claim 12 further comprisinggenerating first and second patterns to apply to first and second setsof radio-frequency (RF) radiating antenna elements, respectively, on anantenna aperture of the electronically steered flat-panel antenna togenerate the first and second beams, respectively, to point at carrierfrequencies that differ in frequency, wherein the RF radiating antennaelements of the first and second sets are different.
 17. The antenna ofclaim 16 wherein the first and second sets of RF radiating antennaelements have a different number of RF radiating antenna elements. 18.The antenna of claim 16 wherein RF radiating antenna elements of thefirst and second sets of RF radiating antenna elements are arbitrarilydistributed on the antenna aperture.
 19. The antenna of claim 12 whereinthe second beam is pointed to a predicted location of the secondsatellite, wherein the predicted location is based on commanded two-lineelements (TLE).
 20. The antenna of claim 12 further comprising: prior togenerating the first beam to track the first satellite, operating theelectronically steered flat-panel antenna in a single-beam configurationin which the electronically steered flat-panel antenna is generating asingle beam, including generating a third beam to track the secondsatellite using a first set of RF radiating antenna elements on anantenna aperture of the electronically steered flat-panel antenna, thefirst set of RF radiating antenna elements including RF radiatingelements of a second set of RF radiating elements on the antennaaperture for generating the first beam and RF radiating elements of athird set of RF radiating elements on the antenna aperture forgenerating the second beam; and determining to switch the electronicallysteered flat-panel antenna to a two-beam configuration in which theelectronically steered flat-panel antenna is generating the first andsecond beams.
 21. A method for use in satellite communication, themethod comprising: engaging in full duplex communication with a firstsatellite, the full duplex communication using a first beam generatedwith a single electronically steered flat-panel antenna; generating asplit beam with the single electronically steered flat-panel antenna andpointing the split beam toward a second satellite track the secondsatellite simultaneously while in full duplex communication with thefirst satellite with the single electronically steered flat-panelantenna, direction of the first and split beams being electronicallycontrolled in two-dimensions using the single electronically steeredflat-panel antenna; and seamlessly handing off traffic from the firstsatellite to the second satellite to maintain connectivity throughouttransition from the first satellite to the second satellite, includingswitching full duplex communications from between the singleelectronically steered flat-panel antenna and the first satellite tofull duplex communications between the single electronically steeredflat-panel antenna and the second satellite.
 22. The method of claim 21further comprising turning off the first beam after handing off trafficfrom the first satellite to the second satellite.
 23. The method ofclaim 21 further comprising: prior to generating the split beam to trackthe second satellite, generating the split beam to acquire a signal fromthe second satellite while generating the first beam.
 24. The method ofclaim 21 further comprising generating first and second patterns toapply to first and second sets of radio-frequency (RF) radiating antennaelements, respectively, on an antenna aperture of the electronicallysteered flat-panel antenna to generate the first and split beams,respectively, to point at carrier frequencies that differ in frequency,wherein the RF radiating antenna elements of the first and second setsare different.